1. Field of Invention
The present invention relates to transmissive screens and rear projectors.
2. Description of Related Art
Rear projectors can be used as suitable displays for home theater monitors and large-screen television sets. Such projectors can be advantageous.
FIG. 7 illustrates an optical system of a rear projector. Referring to FIG. 7, a rear projector 12 has a housing 50 accommodating an optical projection unit 20 that projects an image; a light-guide mirror 30 that guides the image light projected from the optical projection unit 20; and a transmissive screen 42 on which the image light guided by the light-guide mirror 30 is projected.
The transmissive screen 42 applied to this type of rear projector 12 is particularly required to have a wide viewing angle. Japanese Unexamined Patent Application Publication No. 2000-131506 discloses a transmissive screen with such a wide viewing angle. FIG. 8 is a sectional view of a transmissive screen of this type. Referring to FIG. 8, a transmissive screen 900 includes a Fresnel lens portion 910 whose light-exiting face has Fresnel lens components; a microlens array portion 920 whose light-incident face with many microlenses is disposed at the light-exiting face side of the Fresnel lens portion 910; a light shield portion 930 disposed at the light-exiting face side of the microlens array portion 920; and a diffusing sheet 940 disposed at the light-exiting face side of the light shield portion 930.
The transmissive screen 900 has an advantage in that a large vertical viewing angle due to the light refraction effect of the microlenses can be obtained.
However, the transmissive screen 900 has a problem in that light diffraction easily occurs. The transmissive screen 900 also has a problem that moire-fringing easily occurs.